This invention relates generally to mortise locks for use in doors, and more particularly to a mortise lock having a deadbolt, which automatically projects when the door is closed.
A mortise lock is designed to fit into a mortised recess formed in the edge of a door, which is opposite to the edge of the door that is hinged to the doorframe. The mortise lock generally includes a rectangular housing, or case, which encloses the lock components. One of the lock components includes a deadbolt which projects beyond the edge of the door and into an opening or strike plate in the doorframe to lock the door in a closed position. The deadbolt is moveable to a retracted deadbolt position inside the case to permit opening of the door by operation of a latch operator, such as a doorknob or lever handle.
Mortise locks are available that utilize deadbolts that project automatically upon closing of the door. Mortise locks with automatic deadbolts are often used in hotel room doors so that hotel guests do not need to independently and manually throw the deadbolts after closing their hotel room door.
Mortise lock assemblies with automatic deadbolts generally comprise a deadbolt biasing mechanism in the housing of the mortise lock assembly for continually biasing the deadbolt outwardly to the extended deadbolt position. A holding mechanism within the housing holds the deadbolt in a retracted deadbolt position against the force of the biasing mechanism when the door is opened. A trigger mechanism is provided for sensing the strike plate or doorframe when the door is closed. The deadbolt trigger mechanism functions to release the deadbolt holding mechanism so that the deadbolt projects to the extended deadbolt position into an opening in the strike plate or doorframe for locking the door. The deadbolt trigger mechanism is usually associated with an auxiliary latch which is pivotally mounted in the housing for movement from an extended auxiliary-latch position beyond the edge of the door to a retracted auxiliary-latch position in the housing when the auxiliary latch engages the strike plate or door frame. When the latch operator is used to retract the deadbolt for unlocking and opening the door, the deadbolt holding mechanism reengages the deadbolt for holding the deadbolt in the retracted deadbolt position.
Automatic deadbolt mortise lock assemblies often have problems with retaining the deadbolt in the retracted deadbolt position. Inadvertent release of the deadbolt causes the deadbolt to project to the extended deadbolt position before the door is closed. For example, installations where the gap between the front plate of the mortise lock housing through which the deadbolt extends and the strike plate in the door frame is sufficiently large and a room occupant rotates the latch operator sufficiently to allow the deadbolt to clear the opening in the strike plate and then releases the latch operator without a conventional holding mechanism being able to hold the deadbolt in the fully retracted deadbolt position because the auxiliary bolt has not cleared the strike plate, the deadbolt will fully extend outwardly when the door is opened beyond the strike plate. The extended deadbolt creates an undesired security problem as the deadbolt will interfere with the strike plate or doorframe and prevent the door from closing.
For the foregoing reasons, there is a need for a mortise lock that retains the automatic deadbolt in a retracted deadbolt position in the mortise lock assembly when the door is opened, automatically protects the deadbolt when the door is closed, and prevents the projection of the deadbolt when the auxiliary latch has not cleared the strike plate.